In conventional, or regenerative ignition systems, a voltage multiplier and storage device, typically an autotransformer, is cyclically charged from a battery. The stored energy is then distributed to a spark plug through a resistive cable and depleted across a spark gap providing ignition of an air-fuel mixture. Although widely applied, this type of ignition system has many undesirable characteristics. These include; significant energy losses due to the inefficiency of the autotransformer and resistive cable, the transmission of high voltage and energy across a significant distance providing substantial electromagnetic wave emissions, the short reliable life of the autotransformer and resistive cable, the power burden the autotransformer induces on its driving circuitry, the varied quality of the energy delivered to the spark plug due to parametric variation of the autotransformer characteristics, and weight and size of the autotransformer.
Some have attempted to solve some of these problems by providing individual autotransformers mounted on or near each spark plug. This approach still suffers from; significant energy losses due to the inefficiency of the autotransformer, the short reliable life of the autotransformer, the power burden the autotransformer induces on its driving circuitry, the varied quality of the energy delivered to the spark plug due to parametric variation of the autotransformer characteristics, and weight and size of the autotransformer.
Yet others have suggested the use of piezoelectric ignition elements in distributors and individual spark plug applications. One such patent is U.S. Pat. No. 4,412,151, issued Oct. 25, 1983 to Elwood G. Norris. While overcoming the losses inherent to autotransformers these approaches, including the Norris patent, have other problems. For instance, a piezoelectric crystal can generate the required high voltage necessary to ignite a spark gap, however, especially with the advent of lean burn requirements, the ignitable air-fuel ratio's require substantially more energy than a piezoelectric crystal can supply. Additionally, these piezoelectric elements have been driven by energy wasting or inaccurate methods. For instance, piezoelectric elements have been driven by mechanized striking mechanisms. The mechanical type strikers do not compensate for wear and are therefore inaccurate. The electromechanical strikers waste energy to overcome the inertia of a striking mechanism.
All of these approaches suffer from poor efficiency and still have substantial electromagnetic wave emissions.
Earlier attempts at providing electromagnetic shielding on ignition system components have been expensive and difficult to manufacture. An example of an electromagnetic shield is illustrated in U.S. Pat. No. 3,128,139, issued Apr. 7, 1964 to S. E. Estes. The Estes patent shows a tubular electrically conductive housing 13 surrounding an elastomeric boot 20 and is grounded to a hexagonal shoulder 14 of a spark plug 11 by a spring clip 29. This is a complex assembly requiring many individual parts and is difficult to manufacture.
Finally, it's important to note that the operating environment for ignition system components is very hostile from a thermal, vibration and chemical aspect. These components must operate above 135.degree. Celsius, to below 40.degree. Celsius and will be subjected to oil, gasoline, antifreeze, brake fluid, water, salt and other highly corrosive chemicals. The vibration can exceed 5 Gs in 3 axes with transients to thousands of G's. Operating on weighty and bulky components this vibration is fatal. The combination of the vibration, chemicals and thermal range reduces the reliable life of ignition components significantly.
In summary, prior art approaches have many deficiencies including; energy inefficiency, substantial electromagnetic radiation, short reliable life, excessive power burden on the driving circuitry, varied quality of energy provided to the spark gap, lack of sufficient energy for lean burn requirements, excessive weight and size, and insufficient sealing.
What is needed is a considerably smaller, lighter weight, low electromagnetic wave emission, high power, sealed, reliable, high quality of energy, and energy efficient ignition system for internal combustion engines.